1. Field of the Invention
The present invention relates generally to integrated circuit manufacturing equipment, and more particularly but not exclusively to plasma processing systems.
2. Description of the Background Art
A plasma processing system may be used to fabricate integrated circuits. Examples of plasma processing systems include physical vapor deposition, plasma-enhanced chemical vapor deposition, high density plasma chemical vapor deposition, and etching systems. In a plasma processing system, radio frequency (RF) signal source is employed to ignite and maintain plasma inside a process chamber containing one or more substrates. The RF signal source is typically coupled to the process chamber by an electrode, referred to as an xe2x80x9cRF electrodexe2x80x9d. The RF electrode may be located inside a vacuum portion of the plasma processing system such as the interior of the chamber, or in an atmospheric portion near the chamber. Other electrodes, referred to as xe2x80x9cnon-RF electrodesxe2x80x9d, may also be in the same general location as the RF electrodes.
FIG. 1 schematically shows a conventional plasma processing system 100. System.100 includes a process chamber 101 containing a substrate 102. Substrate 102 is supported by a support member 110, which is also inside process chamber 101. An RF signal source 103 drives RF electrodes 121 (i.e., 121A, 121B) with an RF signal required for process chamber 101. RF electrodes 121 are inside support member 110 along with non-RF electrodes 131 (i.e., 131A, 131B), which may be coupled to remotely located electronic modules 151 (i.e., 151A, 151B). Examples of electronic modules 151 include power supplies, controllers, and the like. A non-RF electrode 131 may be connected to a cable 161 (i.e., 161A, 161B) at a terminal 160 (i.e., 160A, 160B). A cable 161 in turn may be connected to a filter 141 (i.e., 141A, 141B), which is connected to an electronic module 151.
If precautions are not taken, RF signal may reach an electronic module 151 by way of a non-RF electrode 131. Accordingly, a filter 141 is typically employed to prevent damaging an electronic module 151. Typically, a filter 141 is a low-pass filter that shunts high frequency signals to ground. A filter 141 is also typically installed near an electronic module 151, which may be several feet away from chamber 101.
In one embodiment, a radio frequency (RF) configuration in a plasma processing system includes an RF electrode driven by an RF signal source and a non-RF electrode coupled to an electronic module. A filter coupled to the non-RF electrode may be configured to provide maximum attenuation at or near an RF signal frequency, while allowing signals associated with the electronic module to pass. The filter may be placed as close to the non-RF electrode as possible. The filter may be, for example, a band stop filter such as a parallel resonant circuit having a resonant frequency at or near an RF signal frequency.
These and other features of the present invention will be readily apparent to persons of ordinary skill in the art upon reading the entirety of this disclosure, which includes the accompanying drawings and claims.